Increasingly, a variety of networks for a variety of modes of communication are being consolidated into a single network for those modes. Previously, phone calls have been transmitted over circuit-switched networks, while electronic messages have been transmitted over data networks, such as the Internet. Multiple devices that reside in the same home have used such disparate networks and thus have not been in communication with one another. To enable this variety of communication modes to share a common network, a number of communication service provider have adopted Session Initiation Protocol (SIP) to initiate or terminate Internet Protocol (IP) services. Some service providers have deployed Internet Protocol Multimedia Subsystem (IMS), an architectural framework for delivering Internet Protocol (IP) multimedia services using SIP as a major protocol, within their IP networks. SIP enabled phone (or IMS enabled phone) calls, electronic messages, and other voice and data communications to be transmitted together over a common data network. An alternative is to rely on the Extensible Messaging and Presence Protocol (XMPP) for these services.
This consolidation of communication modes raises concerns about security. Communications such as phone calls have not previously been exposed to the security weaknesses of data networks. A number of security mechanisms are used for securing communications across data networks, however. Virtual Private Networks (VPNs), for example, have been use to create a secure connection between two devices located remotely from one another and connected via a public data network. These VPNs include network tunnels associated with data packets that have been encrypted using the Internet Protocol Security (IPSec) protocol suite.